Hydraulic resistance apparatus



June 29, 1943. f I o. N. BRYANT 2,323,115

I HYDRAULIC RESISTANCE APPARATUS Filed nay 2o, 1942 Y s sheets-sheet 1 lb aoc.. 'alb F-Low- G'p' M' ATTORNEY June 29, 1943.

o. N. BRYAN'I;

HYDRAULIC RESISTANCE APPARATUS yFiled may zo, 1942 7 :s sheets-sheet 2 Fia. PIMP() A WITNESSES:

le wb INVENTOR MM2 fma 'OzRo MBRYHNT.

BY u l Q/U'LWMW ATTORNEY June 29, 1943. "o, N. BRYANT 2,323,115

HYDRAULIC RESISTANCE APPARATUS Filed my 2o, 1942 s sheetssuny s sa n" INVENTOR 'named .im 29, i943 Pennsylvania Com- acturing Pittsburgh, Pa., a corporation of Anuman my zo, 1942, semi Ne. 442,111

The mvention relates to hydraulic control cirmitsandithasmrmomeetwpmvideaviseous ilow e or orice connectingiirstand sec` 'ondliquidpressurespacesandwhereinthelength ofthe'flowemaybechangedtosccure a proportionate change in the pressure diner-ence of the spaces. Y

, A further object of the invention isV to provide iirst,second andthirdpressurespacesand aviscousiiow passageincludingailrstportion conncctingtheiirstandsecondspacesandasecond portion connecting the second and third spaces, together with means for maintaining liquidunderpresslu'eintheilrstspaceandmeans providing for variation in the length of the viscous iiow passage to secure proportionate variation in pressure in the second space independy ently of -changes inviscosityottheliquid.

There are many places in hydraulic control cir- Acuit.; where it is desirable that the new shan be proportional to the pres'ure diiterence instead of being proportional to the square root of the pressure difference, as is the case with the ordinary sharp-edge oriiice and the like wherein the ilow is turbulent. In these situations. it has been customary to provide long capillary tubes, holes oi.' small diameter, or long annular clearances of small radius; however, such devices are diillcult to adjust to vary the resistance, they clog easily, and are not readily cleaned. In accordance with the present invention, the viscous oriilce or ilow passage is dened between members by a helical or spiral thread on at least one of the members and cooperating with the other member to provide the passage so that, by relative adjustment oi.' the members, the effective length of the helical passage may be varied. Assuming. for example,

'I Claims. (Cl. 138-43) sure of the second space. The viscous ilow passage may be so formed that relative adjustment oi' the members results in change in length of one or both of the portions thereof connecting the rst and second spaces and the second and third spaces, or the lengths oi the portions may be changed oppositely to an equal' extent while maintaining the same total length between the rst and third spaces. I prei'ergto use an arrangement where the same pressure drop and ilow are maintained between the rst and third spaces, while the pressure drop or resistance between the rst and second pressure spaces is varied an amount proportional to the adjustment for the reason that the property of proportionality is not aii'ected by variations in viscosity because such variations ail'ect both ends of the del vice equally.

A further object ofthe invention is to provide a helical or spiral viscous orifice or iiow passage connecting higher. and lower pressure spaces and formed by a thread on at least one of the cooper,- ating members, and wherein the members are relatively adjustable to vary the effective length of the viscous oriice or flow passage.

A further object of the invention is to provide irst, second and third pressure spaces connected by helical or spiral viscous orlnce or ilow passage that the inner member is a screw 1 inch long' and :V4 of an inch in diameter with 10 threads per inch, this is equivalent to a capillary tube 22 inches in length; and, ii' the outer member has its internal threads reamed out to 0.725 diameter, the cross-sectional area of the resulting helical passage is equivalent to a circle whose diameter is .053 inch.

'Ihe helical or spiral viscous oriilce or iow passage deilned by cooperating members may be arranged in a manner analogous to an electrical potentiometer, that is. the passage may connect iirst, second and third pressure spaces, the second space being closed, liquid under pressure being maintained in the irst space, and the members may be adjusted to secure variation in flow passage length between the ilrst and second spaces with the proportionate variation in presportions provided bya pair of members, at least one of the members being threaded and cooperating with the other member to form the helical viscous ilow passage portions, together with means for maintaining liquid under pressure in the ilrst space and means for adjusting the inner member with respect to the outer member to effect adjustment in the length of the viscous oriilce or flow passage portion between the iirst and second spaces to vary the pressure in the latter to an extent proportionate to the variation in iiow passage length.

'Ihese and other objects are eected by the invention as `will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a sectional view of apparatus having the improved viscous orifice applied thereto;

Figs. 2, 3, 4 and 5 are enlarged sectional detail views showing cooperating threads formed to provide helical oriilces;

F18. 6 is a diagram showing relations between flow and pressure drop;

Fig. 7 is a sectional and diagrammatic view showing the potentiometer form of the viscous orifice applied to a governing system;

In Fig. 1, there is shown any suitable housing.

structure I0 having chambers II and I2. Liquid pressure is maintained in the chamber II by any suitable means including the passage I4.

The chambers II and I2 are connected by an orifice device, at I6, comprising an outer member I'I and an inner or plug member I 8. Either or both of the members are threaded to provide a helical viscous orifice or flow passage 2l whose flow area is sufficiently small in relation to its show further forms of length to secure viscous capillary or stream line ilow as distinguished from turbulent flow.

By moving the inner member I8 in or out with respect to the outer member, the effective length of the helical viscous orifice or ilow passage 2| may be varied to secure proportionate variation in pressure drop or resistance thereof to provide, for example, for a pressure in the chamber I2 whichyaries in proportion to the variation in length of the ilow passage. Where only one of the members is threaded, one thereof may be provided with a. threaded stem 22 (Fig. l) for effecting adjustment.

The device so far described is preferable to a needle valve because of the linear relation existing between ilow and pressure drop. Referring to Fig. 6, the relation between ow and pressure l, drop for a viscous orifice is a straight line, the

line a, whereas, for a turbulent ow orifice, the -relation is a curve, curve b, since the flow varies as the square root of thepressure drop. Fig. 6 shows how ineffective the turbulent type becomes at small iiows as compared with the viscous type and shows why time-delay devices or damping devices; such as dashpots, should always use the viscous type of resistance.

Since, withthe viscous type of orifice, the ow varies directly as the pressure drop or resistance,

chamber I2 is P2, then the resistance to ilow is increased or decreased directly in relation to the extent of adjustment of the inner member I8;

and, Pi remaining'the same, P2 may be changedy proportionally to the change in length of the viscous orice or flow passage.

The viscous orifice or flow passage may be providedl by having only one of the inner and outer members threaded (Figs. 1 and 4) or by having both of them threaded,l threads I9 and 20 of Fig. 2, with the top portion of one of the threads removed to leave a helical passage 2|. If` as shown in Fig. 2, the upper portion of one of the threads is removed on a, uniform radius from end to end, the helical passage 2I will be of uniform crosssectional area throughout its length. To secure a larger range of adjustment of resistance. for an adjustment range of the members, as shown in Fig. 3. one of the threads, the thread I9a, may be removed in af tapered manner or along a progressively Changing radius so that the passage 2 Ia, defined with respect to the other thread 20a, tapers in ow area from one end to the other.

Only one of theinner and outer members may be threaded, the thread cooperating with the other member to form the helical viscous flow passage. For. example, in Figs. 1 and 4, the inner member has a thread 20h tting closely the cylindrical bore I9b of the outer member to form the passage. In Fig. 5, the height of the thread 20c progressively increases from one end to the other to provide for a helical passage 2lb tapering in ow area from end to end, as in Fig. 3.

In Figs. '7, 8 and 9 are shown potentiometer arrangements of the orifice device. In these views, the structure I0a is provided with mst, second and third spaces I Ia, I2a and 25, with the second space disposed between the rst and third spaces. As shown, inner and outer, or telescoping, members provide the viscous orifice or flow passage between the rst space II a and the third space 25, the viscous flow passage or orifice comprising a rst portion v2Ic between the rst and second spaces and a second portion 2Id between the second and third spaces.

Assuming that the pressure "P1 in the space IIa is higher than the pressurePa in the space 25 and that the pressure P2 in the space I2a has an intermediate value, then the relation of these pressuresfmay beA changed by adjusting the inner member I8a with respect to the outer member Ila, the., ratio of pressure drops being where N1 is equalto'the number of threads between P1 and P2 an 2 is the number of threads between P2 and P3.

From Fig. 1 0, it'will be apparent that. if Pi changes by angfamount 'APL' then P2 will change by an amount "AP2, and

AP, T52

will equal Nvt-N2 when P3 is constant. With the intermediate pressure chamber closed, this property of proportionality is not affected by variations in viscosity because` such variations affect both ends of thedevice equally since the flows are equal and since the pressure drop varies directly as the iiow, the viscosity andthe length of the helical passage.

In Fig. 8, as Athe inner member I8b is shorter than the outer member I'Ib, it may be adjusted axially Without varying the overall length of the helical passage between Pi and Ps while varying the relative lengths thereof between P1 and P2 and between P2 and P3. Adjustment of the inner member to dispose either end beyond the corresponding end of the outer member has the effect of varying the overall length of the viscous orice or ow passage and of varying the number of threads of one portion with respect to the other.

In Fig. 9, thiere is shown ,Y an arrangement wherein the inner member I8c is longer than the outer member I'Ic. With ythis arrangement, the number of threads N1 between P1 and P2 or the number N2 between P2 and Pa` may be varied While maintaining the total number of threads, Ni-I-Nz constant.

In Fig. 7, there is shown the application of the potentiometer arrangement for speed-correcting adjustment of-"a'governor, the latter including a space, at 26, for fluid under pressure `for the pressure-responsiveapparatus, at 21, for controlling the admission of motive uid to the v outerf` member has a smooth internal bore -l3b .cooperating with the plug thread 26a to provide the ilrst helical visc'ous flow passage portion 2=|c portby an operating member 32 to which force dependent upon speed of the prime mover is applied. y `/l As shown, -the valve 3l is of the-cup type, which cooperates with the seat 34 bounding the port 3U and which defines or bounds an area subject to pressure existing in the spce, at 26. Also, whileany suitable Vmeans may be used to develop and apply to the operating member 32 a force dependent upon speed. as shown, this purpose is achieved by means of an impeller 36 a driven` by the turbine and developing fluid under pressure for the chamber 36. Fluid pressure in the chamber 36 acts on the abutment 33 against the load spring 36 to apply force to the operating member 32. The lower end of the 4load spring 36 is connected to suitable speed changer apparatus. at 4l.-

With a decrease in load, the force dependent upon speed increases and acts on the operating member 32 to cause the valve 3i to restrict the escape of fluid between the latter -and its seat 34 to increase the pressure in the space, at 26,

and` operate the apparatus, at 21, to restrict the supply of motive iluid to the turbine. Increase in space pressure is accompanied by increase in force thereof acting on the cup valve pressure area; and, for a given decrease in load,

the space pressurevincreases until the change in force thereof acting on the cup valve balances the change in force `applied to 'the operating member 32 and corresponding to the decrease -in load. With increase in load, the contrary operation occurs.

The governing arrangement so far described would, of necessity, operate at a/'higher speed at` lno load than at full load, that is, it would inherently have the usual regulation. To provide for reduction in speed change due to load change, the operating member 32 has a piston area 42 equal to and opposed to the cup valve area, and a pressure chamber 43 is provided for the area 42. Passages 44 and 45 provide for communication between the space, at 26, and the chamber 43.A

In Fig. '1, the ilrst pressure space lia, provided by the passage 44, is connected by the viscous i'iow passage portion 2Ic to the second pressure space f I2a, the latter being connected by the second passage 45 to the chamber 43 for the piston face area 42. The third pressure space is shown as being provided by the third or drain passage 46 and is connected to the second space I2a by the second viscous ilow passage portion Zld. A time delay bellows 41 is connected to the second space I2a and it functions to provide delay in changes in pressure in the chamber 43 with respect to changes in the space, at 26, to give stability to the governing apparatus.

, The structure Ia provides the outer member Ila cooperating vwith the inner member or plug 18a.. As already pointed out, either or both of these members may be 'threaded so as to provide the viscous flow passage; and, as shown, the

connecting the Pi pressure space lia to the Pz pressure space i2a, and the second helical viscous now passage l2id connecting the second pressure sp'ace to the P: pressure space 26. By

adJusting the inner member or plug lia to reduce the effective length of the viscous ilow passage between the Pi pressure space lia and the Pz pressure space i2a without changing the length thereof between the Pi and Ps pressure spaces, the pressure Pz increases in relation to the pressure Pi, adjustment of the plug being accomplished, for example, bymeans of the threaded stem 22a. a

In operation, speed correction due to load change is effected by pressure provided in the chamber 43. As this pressure is increased due to shortening of the first viscous orifice or now passage portion 2Ic, the extent 0f correction is increased until, with the pressures in the space, at 26, and in thev chamber 43 equal, isochronous operation is secured.v

'Ihe application of the potentiometer arrangement for controlling the pressure in the chamber 43 is desirable because of the linear relation existing as between plug adjustment and the extent of pressure change. Thus, the pressure in the chamber 43 may be raised and lowered proportionately to the movement of the plug member i60. Changes in viscosity of the liquid do not modify the operation, since a change in the ilrstA orifice portion 2lc is balanced by the same in the second orice portion 2id.

In Figs. 11 to l4,finclusive, there are shown modiiled forms of the viscous oriilce construction wherein, instead of telescopic members,

' i variation, as already described.

plates 60 and 5i are used, the plate 56 having a spiral rib 52 defining a spiral groove 53 of suitably small cross sectional area and which is covered by the plate 5|. The plate 5| is constructed to provide a space communicating with the groove at a point intermediately of the length thereof and the plate incorporates an adjustable feature to provide for oriilce length In Figs. 11 and 12, the inner end of the'spiral groove 53 communicates with the P1 pressure spa-ce IIb and the outer end communicates with the Pa pressure space 25h. The plate 5I is formed witha guideway 56 for the slide 51, the latter providing a space i2b arranged to com.- municate with the spiral groove 53. As the inner face 60 of they slide is flush with the inner face 6| of the plate 5I, both of said inner faces function to cover the spiral groove; however, as the slide 51 is capable of longitudinal adjustment, the space i2b may be brought into communication with the spiral groove at any suitable point along the lengt-h thereof.

If the slide 51 is adjusted longitudinally, the length ofthe viscous orifice -between the pressure spaces P1 and Pz may be increased, while that between the pressure spaces Pz and P: is decreased and vice versa.

In Figs. 13 and 14, variation in viscous orifice lengths is secured by having the plate 56 hinged,

at 63, to the plate 5I and by providing the latter plate with a pressure space I2b communicating with the spiral groove 53. If relative angular motion of the plates is secured, it will be apparent that space i2b may be moved inwardly or outwardly with respect to the plate 50 to vary the viscous orifice lengths between the pressure spaces Pi andV P2 and between Pz and P3. Assuming that relative angular adjustment of the plates has been made to the desired extent, then the plates may be locked together `by any suitable means, for example, by the strap 64 adapted to overlap the plate 50 and having its extremities connected to the plate 5I ,by means of threaded fastenings 65.

The Word .spiral is used hereinin a sense broad enough to embrace helicaLv whereas helical" is used in its narrower geometrical sense.

While the invention has been shown in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and it is desired, therefore, that be placed thereupon as are specifically set forth in the appended claims.

What is claimed is:

1. In hydraulic apparatus, means providing rst, second and third pressure spaces with the second space disposed between the first and third spaces; means for maintaining a first liquid pres sure in said iirst space; means providing a Iirst viscous flow passage connecting the first and second spaces and a second viscous flow passage connectinga the second and third spaces; said rst viscous flow passage ybeing elective to maintain fluid under second pressure in said second space; and means for changing the length of the first -viscous ilow passage to change the second presl to the change in length. 2. In hydraulic apparatus, means providing sure directly in relation first, second and third pressure spaces with the second space disposed between the first and third spaces; means for maintaining a. first liquid pressure in said first space; means providing a rst viscous flow passage connecting the first and second spaces and a second viscous ow passage connecting the second and third spaces; said first viscous flow passage being eiective to maintain fluid under second pressure in said. second space; and means for changing the lengths of the first and second viscous flow passages in opposite directions so as to change the second pressure directly in relation to the change in length of the first viscous flow passage without change in the total length of the rst and second passages connecting the iirst and third spaces.

3. In hydraulic apparatus, means providing first, second and third pressure spaces with the second space disposed between-the rst and third spaces; means for maintaining a first liquid pressure in said rst space; a pair of members; at least one of the members having aspiral thread vcooperating with the other member to provide a.

spiral viscous flow passage including arst portion connecting the rst and second spaces; and a second portion connecting the second and third only such limitations shall spaces; and means providing for relative adjustment of said members to effect change in length of at least one of saidviscous flow passage portions.

4. 'Ihe combination as `claimed in claim 3,

wherein the threaded member is so arranged'with respect to the other member that relative adjustment of the members is eiective to change the lengths of the iirst and second passage portions in opposite directions so as to provide-for change in length of the first portion connecting the rst and second spaces without change in the total length of the first and second portions connecting the first 'and third spaces# 5. In hydraulic apparatus, means providing first, second and third pressure spaces vwith the second space disposed between the rst and third spaces; means for maintaining a first liquid pressure in said i'lrst space; a pair of members; at least one member having a spiral thread cooperating with the outer member to provide a viscous flow passage including a first portion connecting uchange in lviscous ilow the first and second spaces and a second portion connecting the second and third spaces;- means for adjusting the members relatively to effect viscous-flow passage length variation; and means including an accumulator for enclosing the second pressure space.

6. In hydraulic apparatus, means,providing first, second and third pressure spaces withthe.

second space disposed between the ilrst and third spaces; means for maintaining a rst liquid pressure in said rst space; inner and outer members; one of said members having a helical thread and the other member cooperating with the thread to provide a helical viscous flow passage including a first portion connecting the first and second spaces and a second portion' connecting the second and third spaces; and means providing for relative adjustment of the mem-bers to effect passage length. v

7. In hydraulic apparatus, means providing first, second and third pressure spaces with the second space disposed between the first and third spaces; means for maintaining a first liquid pressurein said first space; telescopically-arranged inner and outer members having meshing external and internal threads; one of said threads hav- 

